TEST NAME E. coli SUBSTRATE ENZYME DETECTED WHAT LEADS TO COLOR CHANGE? WHAT DOE
ID: 261628 • Letter: T
Question
TEST NAME
E. coli
SUBSTRATE
ENZYME DETECTED
WHAT LEADS TO COLOR CHANGE?
WHAT DOES A POSITIVE TEST LOOK LIKE?
WHAT DOES A NEGATIVE TEST LOOK LIKE
HOW DO YOU INOCULATE THE MEDIA?
TIPS
Methyl Red (pH indicator) Test:
To determine if glucose can be converted to acidic products (lactate, acetate, formate)
Used to characterize enteric bacteria, (IMViC tests)
Only inoculate 1 MRVP tube. This culture will be split after incubation. ½ of the culture will serve as the MR (methyl red part of the test while the other ½ will be used as the VP (Vogues Proskauer) part. For the MR test add methyl red.
Vogues-Proskauer Test:
To see if glucose can be converted to acetoin.
Used to characterize enteric bacteria, (IMViC tests)
This is run on ½ of the MRVP culture. For the VP test add KOH and alpha-napthol
Motility Test:
Presence of flagella (not a true biochemical test)
Not applicable
Not applicable
Not applicable
Oxidase Test
Urea Utilization:
Detection of urease, which breaks down urea into ammonia.
Triple Sugar Iron (TSI) Agar:
Determine both carbohydrate fermenatation and hydrogen sulfide H2S, production in enteric bacteria
glucose
sucrose
lactose
TEST NAME
E. coli
SUBSTRATE
ENZYME DETECTED
WHAT LEADS TO COLOR CHANGE?
WHAT DOES A POSITIVE TEST LOOK LIKE?
WHAT DOES A NEGATIVE TEST LOOK LIKE
HOW DO YOU INOCULATE THE MEDIA?
TIPS
Explanation / Answer
Test name
E.coli
Methyl Red(pH indicator) test:
To determine if glucose can be converted to acidic products (lactate,acetate,formate)Used to characterise enteric bacteria(IMViC test)
Vogues Proskauer Test:
To see if glucase can be converted to acetoin.Used to characterise enteric bacteria(IMViC TEST)
Urea utilization:
Detection of urease which breaks down urea into ammonia
Test name
E.coli
SUBSTRATE ENZYME DETECTED WHAT LEADS TO COLOR CHANGE WHAT DOES A POSITIVE TEST LOOK LIKE WHAT DOES A NEGATIVE TEST LOOK LIKE HOW DO YOU INOCULATE THE MEDIA TIPSMethyl Red(pH indicator) test:
To determine if glucose can be converted to acidic products (lactate,acetate,formate)Used to characterise enteric bacteria(IMViC test)
Glucose Complete fermentation set of enzymes test organism must produce large quantities of acid from carbohydrate substrate being used Culture medium turns red after addition of methyl red Culture medium remains yellow Inoculate two tubes containing MR-VP broth with a pure culture of microorganisms under investigation,incubate at 35 degree c for up to 4 days add about 5 drops of methyl red indicator to first tube a positive reaction is indicated if the color of the medium changes to red within a few minutes Only incubate 1 MRVP tube.This culture will be split after incubation.half of the culture will bw serve as the MR(methyl red) part of the test while the other half will be used as the VP.For the Mr test add methyl redVogues Proskauer Test:
To see if glucase can be converted to acetoin.Used to characterise enteric bacteria(IMViC TEST)
Glucose-peptone 2,3 Butandiol Production of Acetoin(Acetyl methylcarbinol) which is natural end product from incomplete glucose fermentation Red tube Yellow tube Weigh 5 gram of Glucose,5 g of peptone,and 5 g of dipotassiumhydrogen phosphate separately.Suspend all the ingredients in distilled water.Make up to 1000 ml.pH should be 6.9 Dispense 3 ml of the media into each test tube,which are plugged and sterilized at 121 degree c. This is run on half of the MRVP culture.For the VP test add KOH and alphanaphthol Motility test:Presence of flagella(not a true biochemical test) NOT APPLICABLE Not applicable Not applicable Diffuse zone of growth flaring from the line of inoculation Growth confined to stab line Using isolated colonies from an 18-24 hours culture,inoculate the medium by stabbing the center of the medium to a depth of half inch.Incubate the inoculated medium aerobically at 35 degree c for an 18-24 hours. Motility test medium with Triphenyletrazolium Chloride is used in the same manner.It adds visual emhancement to the bacterial growth Oxidase test TMPD dihydrochloride Cytochrome oxidase Presence of bacteria that produce cytochrome c oxidase,an enzyme of the bacterial electron transport chain. Dark blue to maroon color when oxidised colorless Wet each disk with about four inoculating loops of deionized water.Use a loop to aseptically transfer a large mass of pure bacteria to the disk.Observe the disk for upto three minutes.Urea utilization:
Detection of urease which breaks down urea into ammonia
Urea Urease Hydrolysis of urea produces ammonia and carbon dioxide.The formation of ammonia alkanizes the medium. Color change of phebol red from light orange to magenta (pH 6.8 to Streak the surface of pH 8.1) No color change Streak the surface of urea agar slant with a portion of a well isolated colony or inoculate slant with 1 to 2 drops from an overnight brain heart infusion broth culture.leave the cap on loosely and incubate the tube at 35-37 degree in ambient air for 48 hours to 7 days.Examine the developement of pik color as long as 7 daysRelated Questions
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